Short answer: the same way you do it with any other kind of numbers.
"Place value" means the value of a number comes from where it is (its place) in relation to the decimal point. The digit immediately to the left of the decimal point is the units digit, so tells you the number of units represented.
Each digit to the left of the units digit has a place value that is 10 times that of the digit to its right. Each digit to the right of the units digit (hence to the right of the decimal point) has a place value that is 1/10 that of the digit to its left.
The places have names (see attached).
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You can find the place value of a digit by setting all the other digits in the number to zero. For example, the place value of 2 in the number 324 is 020, or 20.
